Originally Posted by Joe H
You can also change the static compression by using offset timing keys. This will shift the whole cam timing forward or backwards a few degrees, thus changing the valve opening and closing time in relation to crank rotation. This does the same basic thing valve clearance does to timing without loosing the total duration time. Joe

It doesn't alter anything in this discussion but what you are referring to Joe is dynamic compression. Static compression does not change in relation to valve timing.